Aneurysms present a potentially life-threatening problem. An aneurysm is the result of a weak area in a vessel wall, resulting in bulging in the weak area at a particular site in the vessel wall. Untreated aneurysms stand the risk of rupturing, which can result in a stroke or even death. It has become an accepted form of treatment for aneurysms, or for other medical situations where prevention of blood flow to the site of the defect is desired, to occlude the vessel by means of a device implanted into the vessel in question.
Devices for occluding body vessels are known. Occlusion devices that are intended to block blood vessels generally rely on the clotting of blood to provide occlusion. Such devices may include features that promote blood clotting. Nevertheless, it generally takes a variable amount of time for sufficient clotting to have occurred to provide full blockage of a blood vessel. The time taken depends on many factors such as vessel size and pressure and presence or absence of anti-coagulants. It is thus difficult to predict, for any particular patient, by when proper occlusion will have occurred. When such devices are used, a surgeon may not be sure before a patient is discharged from hospital that effective occlusion will occur.
Some prior art occlusion devices take advantage of provision of a physical barrier in a vessel to be occluded. These may take the form of a balloon, or graft material attached to a frame, for example. In such devices, however, the physical barrier is generally not well anchored within a vessel, and is subject to displacement after implantation.